Theory of Happiness
by SoranoKuma
Summary: Eren was about to be married to Mikasa as he felt that it was the right things to do, without realizing his own heart and without knowing there was someone who had always been in love with him for all this time. What will happened to his marriage? What happened when he met that person again, the person who had loved him for all this time?


Theory of Happiness

"Are you sure, you're going to marry Mikasa?" again his blonde friend, Armin, asked him the question repeatedly to him, trying to re-assure him about his decision of marrying his own best friend.

There was no answer at all from him as he knew that was for the best, for him and for her. However, his best friend knew that it was not what Eren wanted from the bottom of his heart. He knew that Eren actually didn't love Mikasa romantically, but he loved her as a _family_ and he misinterpreted it as a _romantic _love, even though it was different. Armin had told him countless time about his kind of love to his best friend, but it was no avail to him as Eren kept on persisting about how sure he was to Mikasa.

'_Eren, would you regret your choice? Even you have decided your marriage day.'_ Inside of Armin's heart kept on trying to scream out loud to tell Eren about everything that was inside his mind, but again, he knew Eren would not listen to him at all.

"Eren, you don't love Mikasa as the way she is. You _don't_, Eren." Again he tried to explain things to him, but Eren had already closed his ears for him and even if he screamed, the brunette would not listen to him at all.

Eren sighed on his friends complained about him going to marry Mikasa and Armin knew that Eren wanted to marry Mikasa not because of love, but because of convenience. He knew that it was the right things to do, which made him failed to see there was someone who really _loved_ him deeply from the start and this hasty decision hurt him the most as he would never be together with the one that he clearly loved.

"You know, Eren, there is someone who loves you the most out there too." Armin told him before going out from the room to the hallway; he tried to give Eren the hint about this person, who loved him the most that he would even throw away his life just in order to save him.

'_Eren, please get it. Please…He loves you so much that he would throw away everything in order to have you.'_ Armin's heart screaming to the top of his head, but there was no sound – no voiced out to tell him who it was at all.

'_Please, don't do this, Eren. You never know what you have until you lose it, Eren. You just never know it, Eren.'_ Again the words died inside of his heart – inside of his _mind_ without him being able to tell him at all about that person – about this _person_.

* * *

_ "I want a quick marriage." _Again the person who had dark hair told the brunette when they were doing an interview for something.

_ "To be honest, Eren would probably be the one who get married first." _Again the his voice came out as if he was complaining about something that Eren didn't understand at all – about something that he was so _clueless_ about.

And it was about his _love_ to him. It was about his _love_ that the person whom he loved the most was so clueless about. He kept on saying things about marriage and how his _loved_ one would be the first one to get married, yet his _precious_ person didn't understand it at all – his _dearest_ person didn't get his intention at all.

"No, you don't understand it at all, Eren." He said to himself as he coordinated his paperwork before he left his office as he had done everything that he needed for his work.

'_I love you.' _Again the words died on his lips – on his mouth.

He sighed as there was no answer to his silent confession at all. Even his loved one didn't understand his love at all – he didn't _understand _how much he wanted to have him to himself at all.

"I love you," again the confession died on his lips as he looked back to his office that were filled with memories of his reincarnated squad and him – him, whom he loved but he would never love him back at all.

"I love you, Eren. Even if you don't love me back at all." He ended his sad words even though he knew that no one would ever answer him at all.

* * *

It was the day of his wedding and there were many people attending the brunette's wedding with his _beloved_ person, Mikasa. They were there, cheering for both couple that would become one soon enough, even though it was not because of _love_ – it was because of convenience at all.

"I, _Eren Jaeger_, take you, _Mikasa Ackerman_, to be my lawfully wedded wife, to have and to hold, from this day forward, for better, for worse, for richer, for poorer, in sickness and in health, until death do us part." The vow that would tie them together for lifetime was told by Eren, who was going to be his would be husband.

The black-haired woman in front of him smiled to him as he would willingly take her as his wife. However, she knew that he was not love with her at all. He was just _loved_ her but not _fallen in love_ with her at all, which was a completely different things for her. And she knew, it would affect everything in their marriage later.

"Eren, I don't want to be just _good enough_ for you." She said to him with a smile on her face as she looked at his confused look towards her.

"I don't want you to _love_ me only; I want you to be _in love _with me, Eren." Again she told him about what she had been thinking when Levi told her before she went to Eren.

He was shocked with what Mikasa told him all of a sudden as he was so sure that he _loved_ her as much as she loved him back. He didn't understand what was happening at all with him and with the woman in front of him.

"But, I'm in love with…" there was a paused and all of them were silent as they waited for his continuation…which there were none of it at all – there were no continuation at all to what he was about to say as they both realized whose Eren's heart really _belong_ to…

* * *

Months passed as he called off his wedding with Mikasa, whom he was supposed to be married with, and after those months, he had never seen Levi anywhere at all. Until one day, he bumped into someone when he was on the way home.

"I'm sorry! Are you okay?" he asked him as he could not see his face clearly.

The man slowly stood up and picked up all of his things back again without answering the younger man's voice at all. Eren helped him picking up his things and caught a glimpse of the older man's face.

"Levi!" he was surprised when he knew the man in front of him was the man he had been _looking_ for his whole life again after his wedding.

The man looked at him and again, with a slight sad expression, he called the man's name, whom he had bumped onto before.

"Ah, Eren. How are you?" he asked him with a silent tone, trying to cover up all of his emotions as he knew the man in front of him was someone else – he _was_ someone else.

The emerald eyes smiled to him as he knew that he had found the person he had been looking for after the long thinking during the wedding, which was finally called off after he had uncovered his feelings for this person – for this _particular_ person. Who named was _Levi_.

"I'm doing well and I've got to go. I'm sorry…_Eren_." The way he called his name was slow as if he was really in pain for something and tried to cover it up with many things.

However, before he could take a few steps away from Eren, the brunette walked towards him instead of the opposite way where he was supposed to be going to. He walked a few steps behind him and called _his_ name.

"L-Levi!" he called the man's name, but there was no answer at all nor he turned his back to him.

Eren kept on looking at the raven-haired's back as he tried to catch the words he wanted to say to him – the words he had been waiting for come out for such a long time.

"Would you…" there was a paused before he could continue his words.

"Would you live together with me, Levi?" the words came out from the younger man's mouth and it satisfied him. He was happy that he could say that to the man, whom he had loved for such a long time – for such _a long time_.

There was no answer from the man in front of him at all as he kept on waiting for the answer. He didn't know what he should do at all and all he could do was waiting for him to answer him back, even though he knew that Levi would be able to reject him after all this time.

"Yes." The answer came out and it was just a short answer from the man whom he had been waiting for all this time.

Eren looked at him in surprise as the shorter man turned his back from him, facing him with his blue orbs slowly filled with tears that formed on the edge.

"Yes, Eren, I would." Again another answer came out from his mouth as he walked closer to the taller man that froze on his spot.

Levi came closer to him and hugged him, he hugged him tight as if he would never let him go at all – he would never _let him go_ at all for his entire life. "Yes, I would love too." Another answer came out again as he tried to reassure Eren with his answer.

The younger man smiled – he smiled and hugged him back as if he had never hugged him before. He was happy. He was happy to know that he had found the _real_ happiness that he had been looking for all his life. He was so grateful as he had found his _only_ happiness in this world.

"Thank you. Thank you, Levi." He replied him back with smile on his face as he kept on hugging him.

"I love you. I love you, Levi." He confessed to him as he kept on repeating countlessly his confession to the shorter man, whom he had hurt before.

Warm and happy were the only things Levi could describe from Eren's hug. He was so happy as he had never thought the man he loved would return his love back at all. He was happy – he was so relieved for that.

"I love you too, Eren. I have always loved you…" again he confessed to him, but now, he knew the answer to his confession – he knew the _answer_ to his silent confession to the man he loved, which was…

"Yes, I love you too." Was the only answer Eren could give to him as Levi slowly kissed him on the lips.

"I love you too, Levi." As he finally understood the real theory of the true happiness he had found for all his life.

* * *

.

.

.

_"I love you too, my beautiful brat. I always do," he said with smile on his face as he opened the veil that was covering Eren's beautiful face in front of him._

_With smile, Eren replied him back as he put the ring on his beloved husband._

_ "I do too, Levi."_

* * *

**Seriously, I did it today and I finished it today too. I have been doing it in my class too. I hope that those who sit behind me doesn't read it at all. *praying***  
**Anyway, this is from what this fabulous person! I give my credit for her too, as she gave the inspiration for this one. :3**  
**Thank you very much: titanjaeger! :3**  
**Please check this person's tumblr too! It is on the link above!**  
**Thanks a lot!**  
**- Soranokuma**

**P.S: I'm sorry, I know it is pretty lame. I'm so sorry! Please review if you like to! Thanks a lot!**

**P.S: The link is on my AO3. If you want to check it out, please go to my AO3 link on my profile. Thanks!**


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